King et al. U.S. Pat. No. 3,798,256 discloses the hydrocyanation of 3-pentenenitrile to produce adiponitrile using nickel complexes as catalysts and organic boron compounds as promoters. Such hydrocyanation reactions produce catalyst residues which are primarily Ni(NCR).sub.4 (NCBAr.sub.3).sub.2 hereinafter referred to as NCBCs. Shook U.S. Pat. No. 4,082,811 discloses treating such residues with ammonium hydroxide to precipitate the amine adduct of triarylborane. The triarylborane can be recovered from the adduct by treatment with metal hydroxide--see Shook U.S. Pat. No. 4,134,923.
The present invention is a direct method of recovery of the triarylborane promoter from the catalyst residue.